This invention relates in general to an apparatus for detecting the orientation of an object, and particularly to a tilt switch for detecting a particular orientation.
Tilt switches and jitter switches are used in portable electronic devices, such as radio transceivers and paging units, to detect whether the unit is in an non-vertical orientation, and to detect movement of the device. Tilt switches may be used for generating a signal when non-vertical orientation is detected, for example in "mandown" situations where police officers are injured. Further, tilt switches operating as jitter switches can be used for detecting continued motion of a portable device, the lack of such motion typically causing the generation of an alert signal.
A conventional tilt switch includes a glass envelope that contains a ball of mercury. A pair of electrodes are situated at one end of the envelope and the mercury forms an electrical contact between the electrodes when the switch is oriented so that the mercury extends to the ends of the envelope containing the electrodes, thus forming an electrical contact therebetween. In certain applications, it is important to measure whether an electronic device is oriented upwards, downwards, or at an angle in between. For some applications, it is possible to use a number of conventional tilt switches together, where each tilt switch is mounted at a different orientation so that the closing or opening of particular switches indicates the relative orientation of the device. However, the use of several individual tilt switches may take up significant real-estate in the device, and the individual switches must typically be mounted in precise orientation relative to each other in order for the combination of tilt switches to be effective.
Therefore, there is a need for a single tilt switch that can detect one of several orientations. Such a tilt switch should take up less volume within the device, and require that the orientation of only the single tilt switch within the device be precisely established, rather than the orientation of a number of switches.